1. Field of the Invention
The present invention generally relates to a voltage sensor for dual-wire power cable, and more particularly, to a non-contact type voltage sensor for dual-wire power cable, which can compensate the vertical displacement and the horizontal displacement generated during the voltage sensor being installed on the dual-wire power cable by the iterative operation process in order to achieve “Install & Measure”. The present invention further relates to the method for compensating installation position variation of the voltage sensor.
2. Description of the Related Art
Currently, owing to the awareness of the environmental protection, people pay more attention to how to save more energy. Thus, how to measure the electricity consumption, voltage and current of various household electric appliances has become an important issue. However, conventional voltage sensors still have some shortcomings to be overcome.
For example, the clamp-on voltage and current meter can be directly installed on the power cables of various household electric appliances to their electricity consumption, including voltage, current and watt; therefore, users can easily acquire the electricity consumption information of various household electric appliances in order to control the possible electricity consumption and achieve energy saving. However, the user should manually install the clamp-on voltage and current meter on the power cable; therefore, the installation position may vary with the manual operation of the user, which will result in measurement error. Accordingly, the power consumption information measured by the clamp-on voltage and current meter may be incorrect.
U.S. Pat. No. 8,680,845 discloses a non-contact current and voltage sensor, which can be directly installed on the power cables of various household electric appliances to measure their currents and voltages. The sensor can achieve “Install & Measure”. However, it fails to provide a reliable calibration method to calibrate the errors due to the installation position variation caused by manual installation. Thus, the voltage and current measured by the sensor will always have errors.
U.S. Pat. No. 5,473,244 discloses an apparatus for measuring voltages and currents using non-contacting sensors, which can use the feedback signal to calibrate the measured current and voltage in order to improve its accuracy. However, the apparatus will still be influenced by the installation position variation, so the voltage and current measured by the apparatus are still inaccurate.
U.S. patent Pub. No. 20140021965 discloses a high voltage measurement system, which takes the power cable to be measured as a part of the measurement system and uses the temperature compensation technique to enhance the accuracy of the measurement system. Similarly, it still fails to provide a reliable method to calibrate the errors due to the installation position variation caused by manual installation. Thus, the measurement result of the measurement system may still have some errors.
U.S. patent Pub. No. 20130293218 discloses an optical sensor for non-contact voltage measurement, which uses an optical sensor to measure the optical signal which can represent the AC voltage of the power cable. However, it still fails to provide a reliable calibration method to calibrate the errors due to installation position variation caused by manual installation. Accordingly, the voltage and current measured by the sensor will always have errors.
TW patent Pub. No. 201319605 discloses a proximity current sensing apparatus, which allows the user to manually calibrate the errors due to installation position variation caused by manual installation. The apparatus can effectively calibrate the errors due to installation position variation caused by manual installation; however, the user should manually operate the apparatus to calibrate the errors due to the installation position variation caused by manual installation, which is very inconvenient for the user.
Therefore, it has become an important issue to provide a voltage sensor capable of solving the problem that the conventional voltage sensors cannot automatically calibrate the errors due to installation position variation caused by manual installation.